Resist composition for immersion exposure and method of forming resist pattern

ABSTRACT

A resist composition for immersion exposure and a method of forming a resist pattern which can satisfy both of excellent resistance to an immersion medium and lithography properties. The resist composition for immersion exposure includes a resin component (A) which exhibits changed alkali solubility under action of acid and an acid-generator component (B) which generates acid upon irradiation, the resin component (A) including a resin (A1) which contains a fluorine atom and a resin (A2) which has a structural unit (a′) derived from acrylic acid and contains no fluorine atom, and the amount of the resin (A1) contained in the resin component (A) being within the range from 0.1 to 50% by weight.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/094,399, filed May 20, 2008, which is the U.S. National Phase filingunder 35 U.S.C. §371 of PCT/JP2006/324573, filed Dec. 8, 2006, whichdesignated the United States and was published in a language other thanEnglish, which claims priority under 35 U.S.C. §119(a)-(d) to JapanesePatent Application No. 2005-357493, filed Dec. 12, 2005, and JapanesePatent Application No. 2006-006013, filed Jan. 13, 2006. The contents ofthese applications are incorporated herein by reference in theirentireties.

TECHNICAL FIELD

The present invention relates to a resist composition for use inimmersion exposure (immersion exposure), and a method of forming aresist pattern.

BACKGROUND ART

Lithography methods are widely used in the production of microscopicstructures in a variety of electronic devices such as semiconductordevices and liquid crystal devices, and ongoing miniaturization of thestructures of these devices has lead to demands for furtherminiaturization of the resist patterns used in these lithographyprocesses. With current lithography methods, using the most up-to-dateArF excimer lasers, fine resist patterns with a line width ofapproximately 90 nm are able to be formed, but in the future, even finerpattern formation will be required.

In order to enable the formation of these types of ultra fine patternsof less than 90 nm, the development of appropriate exposure apparatusand corresponding resists is the first requirement.

With respect to resists, chemically amplified resists, which enable highlevels of resolution to be achieved, are able to utilize a catalyticreaction or chain reaction of an acid generated by irradiation, exhibita quantum yield of 1 or greater, and are capable of achieving highsensitivity, are attracting considerable attention, and development ofthese resists is flourishing.

In positive chemically amplified resists, resins having aciddissociable, dissolution inhibiting groups are the most commonly used.Examples of known acid dissociable, dissolution inhibiting groupsinclude acetal groups such as ethoxyethyl groups, tertiary alkyl groupssuch as tert-butyl groups, as well as tert-butoxycarbonyl groups andtert-butoxycarbonylmethyl groups. Furthermore, structural units derivedfrom tertiary ester compounds of (meth)acrylic acid, such as2-alkyl-2-adamantyl (meth)acrylates, are widely used as the structuralunits containing an acid dissociable, dissolution inhibiting groupwithin the resin component of conventional ArF resist compositions, asdisclosed in Patent Document 1 listed below.

On the other hand, with respect to the exposure apparatus, techniquessuch as shortening the wavelength of the light source used, andincreasing the diameter of the lens aperture (NA) (namely, increasingNA) are common. For example, for a resist resolution of approximately0.5 μm, a mercury lamp for which the main spectrum is the 436 nm g-lineis used, for a resolution of approximately 0.5 to 0.30 μm, a similarmercury lamp for which the main spectrum is the 365 nm i-line is used,for a resolution of approximately 0.3 to 0.15 μm, 248 nm KrF excimerlaser light is used, and for resolutions of approximately 0.15 μm orless, 193 nm ArF excimer laser light is used. In order to achieve evengreater miniaturization, the use of F₂ excimer laser (157 nm), Ar₂excimer laser (126 nm), extreme ultraviolet radiation (EUV: 13 nm),electron beam (EB), and X-ray and the like is also being studied.

However, shortening the wavelength of the light source requires a newand expensive exposure apparatus. Furthermore, if the NA value isincreased, since the resolution and the depth of focus exist in atrade-off type relationship, even if the resolution is increased, aproblem arises in that the depth of focus is lowered.

Against this background, a method known as immersion exposure (immersionlithography) has been reported (for example, see Non-Patent Documents 1to 3). In this method, exposure (immersion exposure) is conducted in astate where the region between the lens and the resist layer formed on awafer, which has conventionally been filled with air or an inert gassuch as nitrogen, is filled with a solvent (a immersion medium) that hasa larger refractive index than the refractive index of air.

According to this type of immersion exposure, it is claimed that higherresolutions equivalent to those obtained using a shorter wavelengthlight source or a larger NA lens can be obtained using the same exposurelight source wavelength, with no lowering of the depth of focus.Furthermore, immersion exposure can be conducted using existing exposureapparatus. As a result, it is expected that immersion exposure willenable the formation of resist patterns of higher resolution andsuperior depth of focus at lower costs. Accordingly, in the productionof semiconductor devices, which requires enormous capital investment,immersion exposure is attracting considerable attention as a method thatoffers significant potential to the semiconductor industry, both interms of cost and in terms of lithography properties such as resolution.Currently, water is mainly used as the immersion medium for immersionlithography.

Patent Document 1

-   Japanese Unexamined Patent Application, First Publication No. Hei    10-161313-   [Non-Patent Document 1] Journal of Vacuum Science & Technology B    (U.S.), 1999, vol. 17, issue 6, pp. 3306 to 3309.-   [Non-Patent Document 2] Journal of Vacuum Science & Technology B    (U.S.), 2001, vol. 19, issue 6, pp. 2353 to 2356.-   [Non-Patent Document 3] Proceedings of SPIE (U.S.), 2002, vol. 4691,    pp. 459 to 465.

DISCLOSURE OF INVENTION Means to Solve the Problems

However, many factors associated with immersion exposure remain unknown,and the formation of an ultra fine resist pattern of a level suitablefor actual use remains problematic. For example, in immersionlithography, as described above, the immersion medium comes in contactwith the resist film and the lens. As a result, lithography propertiesmay be adversely affected by elution of a substance contained in theresist into the immersion medium, which cause degeneration of the resistfilm and lowering of the performance thereof, local change in therefractive index of the immersion medium caused by the eluted substance,and staining of the lens surface by the eluted substance. Therefore,problems are likely to occur including deterioration in the sensitivity,formation of T-top shaped resist patterns, roughening of the surface ofthe resist pattern, or swelling of the resist pattern.

As a technique for solving the above-described problems, improving theresistance of the resist film to the immersion medium can be considered.Currently, since aqueous solvent such as water is mainly considered asthe immersion medium, it is presumed that enhancing the hydrophobicityof the resist film is effective in improving the resistance to theimmersion medium.

However, changing the composition of the resist for enhancing thehydrophobicity of the resist film generally results in deterioration ofthe lithography properties. Therefore, achieving both of resistance tothe immersion medium and lithography properties is difficult.

The present invention takes the above circumstances into consideration,with an object of providing a resist composition for immersion exposureand method of forming a resist pattern, which can achieve both ofexcellent resistance to an immersion medium and excellent lithographyproperties.

Means to Solve the Problems

As a result of studies of the present inventors, it has been found thatthe above-mentioned problems can be solved by using a combination of anacrylate resin and a fluorine atom-containing resin in a specificamount. The present invention has been completed based on this finding.

Accordingly, a first aspect of the present invention is a resistcomposition for immersion exposure including a resin component (A) whichexhibits changed alkali solubility under action of acid and anacid-generator component (B) which generates acid upon irradiation, theresin component (A) including a resin (A1) which contains a fluorineatom and a resin (A2) which has a structural unit (a′) derived fromacrylic acid and contains no fluorine atom, and the amount of the resin(A1) contained in the resin component (A) being within the range from0.1 to 50% by weight.

A second aspect of the present invention is a method of forming a resistpattern, including: applying a resist composition for immersion exposureof the first aspect to a substrate to form a resist film on thesubstrate; subjecting the resist film to immersion exposure; anddeveloping the resist film to form a resist pattern.

In the present invention, the term “structural unit” refers to a monomerunit that contributes to the formation of a polymer (resin).

An “alkyl group” includes a linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified.

A “lower alkyl group” is an alkyl group of 1 to 5 carbon atoms.

The term “exposure” is used as a general concept that includes not onlyirradiation of light, but also irradiation with any form of radiationsuch as electron beam.

Effect of the Invention

According to the present invention, there are provided a resistcomposition for immersion exposure and method of forming a resistpattern, which can achieve both of excellent resistance to an immersionmedium and excellent lithography properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram of receding angle and sliding angle.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in detail.

<<Resist Composition for Immersion Exposure>>

A resist composition for immersion exposure according to the presentinvention includes a resin component (A) (hereafter referred to as thecomponent (A)) which exhibits changed alkali solubility under action ofacid and an acid-generator component (B) (hereafter, frequently referredto as “component (B)”) which generates acid upon exposure.

In the present invention, it is necessary that the resin component (A)include a resin (A1) which contains a fluorine atom and a resin (A2)which has a structural unit (a′) derived from acrylic acid and containsno fluorine atom, and the amount of the resin (A1) contained in thecomponent (A) be within the range from 0.1 to 50% by weight.

The resist composition for immersion exposure according to the presentinvention may be either a so-called negative composition, or a so-calledpositive composition. The resist composition of the present invention ispreferably a positive resist composition.

When the resist composition for immersion exposure according to thepresent invention is a negative resist composition, the component (A) isan alkali-soluble resin, and a cross-linking agent (C) is blended withthe resist composition.

With respect to the negative resist composition, during resist patternformation, when acid is generated from the component (B) upon exposure,the action of this acid causes cross-linking between the alkali-solubleresin and the cross-linking agent, and the cross-linked portion becomesalkali insoluble.

As the alkali-soluble resin, it is preferable to use a resin having astructural unit derived from at least one of α-(hydroxyalkyl)acrylicacid and a lower alkyl ester of α-(hydroxyalkyl)acrylic acid, as itenables formation of a satisfactory resist pattern with minimalswelling. Here, the term “α-(hydroxyalkyl)acrylic acid” refers to one orboth of acrylic acid in which a hydrogen atom is bonded to the carbonatom on the α-position having the carboxyl group bonded thereto, andα-hydroxyalkylacrylic acid in which a hydroxyalkyl group (preferably ahydroxyalkyl group of 1 to 5 carbon atoms) is bonded to the carbon atomon the α-position.

As the cross-linking agent (C), typically, an amino-based cross-linkingagent such as a glycoluril having a methylol group or alkoxymethyl groupis preferable, as it enables formation of a resist pattern with minimalswelling. The amount of the cross-linking agent (C) added is preferablywithin the range from 1 to 50 parts by weight, relative to 100 parts byweight of the alkali-soluble resin.

When the resist composition for immersion exposure according to thepresent invention is a positive resist composition, as the component(A), a resin having acid dissociable, dissolution inhibiting groups andexhibiting increased alkali solubility under action of acid is used.With respect to the positive resist composition, during resist patternformation, when acid is generated from the component (B) upon exposure,the acid dissociable, dissolution inhibiting groups are dissociated bythe generated acid, and the component (A) becomes alkali soluble.Therefore, in the formation of a resist pattern, by conducting selectiveexposure of the resist composition applied onto a substrate, the alkalisolubility of the exposed portions is enhanced, and hence, a resistpattern can be formed by alkali developing.

[Resin (A1)]

As the resin (A1), there is no particular limitation as long as it is aresin containing a fluorine atom, and one or more kinds ofalkali-soluble resins or resins capable of becoming alkali-soluble,which have conventionally been proposed as a chemically amplifiedphotoresist can be exemplified. When the former is used, the resistcomposition becomes a negative type, and when the latter is used, thecomposition becomes a positive type.

In either case of a positive type or a negative type, it is preferablethat the resin (A1) have a fluorinated hydroxyalkyl group, as theeffects of the present invention become superior.

The term “fluorinated hydroxyalkyl group” refers to a hydroxyalkyl groupin which some of the hydrogen atoms are substituted with hydroxy groups,wherein some or all of the remainder of the hydrogen atoms within thealkyl group (hydrogen atoms within the alkyl group which have not beensubstituted with hydroxyl groups) are substituted with fluorine atoms.In a fluorinated hydroxyalkyl group, the hydrogen atom of the hydroxygroup can be easily released due to the fluorination.

In the fluorinated hydroxyalkyl group, the alkyl group is preferablylinear or branched. The number of carbon atoms of the alkyl group is notparticularly limited, but is preferably from 1 to 20, more preferably 4to 16, and most preferably 4 to 12. The number of hydroxy groups is notparticularly limited, but is preferably 1.

Among these, as the fluorinated hydroxyalkyl group, groups in which afluorinated alkyl group and/or a fluorine atom is bonded to the carbonatom having the hydroxy group bonded thereto (i.e., the carbon atom onthe α-position within the hydroxyalkyl group) are preferable.

Especially, the fluoroalkyl group bonded to the α-position is preferablya perfluoroalkyl group in which all of the hydrogen atoms of the alkylgroup have been substituted with fluorine atoms.

In the present invention, it is particularly desirable that the resin(A1) have a group represented by general formula (I) shown below.

wherein x represents an integer of 0 to 5; and y and z eachindependently represents an integer of 1 to 5.

In general formula (I) above, x is preferably an integer of 0 to 3, andit is particularly desirable that x be 0 or 1.

It is preferable that y and z each independently represents an integerof 1 to 3, and most preferably 1.

In either case of a positive type or a negative type, the resin (A1)preferably has a structural unit (a) derived from acrylic acid.

In the present description and the claims, the concept of “acrylic acid”includes acrylic acid (CH₂═CHCOOH) in a narrow sense and derivativesthereof in which some or all of the hydrogen atoms are substituted withother groups or atoms.

Examples of acrylic acid derivatives include α-substituted acrylic acidswhich are acrylic acid in a narrow sense having a substituent (an atomor group other than a hydrogen atom) bonded to the carbon atom on theα-position, and acrylate esters of such α-substituted acrylic acids inwhich the hydrogen atom within the carboxy group is substituted with anorganic group.

As the organic group within the acrylate ester, there is no particularlimitation, and examples thereof include groups bonded to the side-chainportion of the acrylate ester (e.g., groups having a fluorinated alkylgroup and an aliphatic monocyclic/polycyclic group, acid dissociable,dissolution inhibiting groups, lactone ring-containing groups, polargroup-containing aliphatic hydrocarbon groups and aliphatic polycyclichydrocarbon groups) within the structural units (a0) to (a4) describedbelow.

The “α-position (the carbon atom on the α-position)” of acrylic acidrefers to the carbon atom having the carbonyl group bonded thereto,unless specified otherwise.

Examples of the substituent within the α-substituted acrylic acidinclude a halogen atom, a lower alkyl group and a halogenated loweralkyl group.

Examples of halogen atoms for the substituent at the α-position includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable.

Specific examples of the lower alkyl group for the substituent at theα-position include linear or branched lower alkyl groups such as amethyl group, ethyl group, propyl group, isopropyl group, n-butyl group,isobutyl group, tert-butyl group, pentyl group, isopentyl group, andneopentyl group.

The “lower alkyl group” within the halogenated alkyl group for thesubstituent at the α-position is the same as the lower alkyl groupsdescribed above. The halogen atom within the halogenated alkyl group isthe same as the halogen atoms described above.

The substituent bonded to the α-position of acrylic acid is preferably ahydrogen atom, a halogen atom, a lower alkyl group or a halogenatedlower alkyl group, and more preferably a hydrogen atom, a fluorine atom,a lower alkyl group or a fluorinated lower alkyl group. In terms ofindustrial availability, a hydrogen atom or a methyl group isparticularly desirable.

The term “structural unit derived from acrylic acid” refers to astructural unit which is formed by the cleavage of the ethylenic doublebond of acrylic acid.

The term “structural unit derived from an acrylate ester” refers to astructural unit which is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

As the structural unit (a), a structural unit represented by generalformula (a) shown below can be exemplified.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; and X represent a hydrogenatom or a monovalent organic group.

As the halogen atom, lower alkyl group and halogenated lower alkyl groupfor R, the same as the halogen atom, lower alkyl group and halogenatedlower alkyl group for the above-mentioned substituent at the α-positioncan be exemplified.

As the organic group for X, the same as the “organic group within theacrylate ester” described above can be exemplified.

In the resin (A1), the amount of the structural unit (a) based on thecombined total of all structural units constituting the resin (A1) ispreferably from 50 to 100 mol %, and more preferably 70 to 100 mol %. Itis particularly desirable that the resin (A1) consist of the structuralunit (a) derived from acrylic acid, as it becomes particularlyadvantageous in terms of the effects of the present invention.

Here, the expression “consist of the structural unit (a)” means that themain chain of the resin (A1) is constituted from only the structuralunit (a), and does not contain any other structural units.

In the present invention, it is preferable that the resin (A1) have astructural unit (a0) derived from an acrylic ester having on the sidechain portion thereof a fluorinated hydroxyalkyl group and an aliphaticmonocyclic/polycyclic group (aliphatic cyclic group).

In the present description and the claims, the term “side chain portion”refers to the portion which does not constitute the main chain. As thestructural unit (a0), structural units in which X in general formula (a)above is a group having both of a fluorinated hydroxyalkyl group and analiphatic monocyclic/polycyclic group can be exemplified.

With respect to the “aliphatic cyclic group”, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The aliphatic cyclic group may be monocyclic or polycyclic. The term“aliphatic monocyclic group” refers to a monocyclic group that has noaromaticity, and the term “aliphatic polycyclic group” refers to apolycyclic group that has no aromaticity.

The aliphatic cyclic group may be a hydrocarbon group (alicyclic group)consisting of carbon and hydrogen, or a heterocyclic group in which someof the carbon atoms constituting the ring of the alicyclic group arereplaced by hetero atoms such as oxygen atoms, nitrogen atoms or sulfuratoms. The aliphatic cyclic group is preferably an alicyclic group.

The aliphatic cyclic group may be either saturated or unsaturated, butis preferably saturated, as it exhibits high transparency to ArF excimerlasers and the like, and is superior in resolution, depth of focus (DOF)and the like.

The number of carbon atoms of the aliphatic cyclic group is preferablyfrom 5 to 15.

As aliphatic monocyclic groups, groups in which two or more hydrogenatoms (including the hydrogen atom substituted with the fluorinatedalkyl group; the same applies below) have been removed from amonocycloalkane can be exemplified. Specific examples of such aliphaticmonocyclic groups include groups in which two or more hydrogen atom hasbeen removed from cyclopentane or cyclohexane, and groups in which twohydrogen atom has been removed from cyclohexane is preferable.

As aliphatic polycyclic groups, groups in which two or more hydrogenatom has been removed from a bicycloalkane, tricycloalkane ortetracycloalkane can be exemplified. Specific examples of such aliphaticpolycyclic groups include groups in which two or more hydrogen atom hasbeen removed from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

As the polycyclic group, any of the multitude of conventional polycyclicgroups constituting acid dissociable, dissolution inhibiting groupswithin a resin for resist compositions used in an ArF excimer laserprocess can be appropriately selected.

In terms of industrial availability, cyclohexane is preferable as themonocyclic group, and a group in which two or more hydrogen atom hasbeen removed from adamantane, norbornane or tetracyclododecane ispreferable as the polycyclic group, and a group in which two or morehydrogen atom has been removed from norbornane is particularlydesirable.

In the present invention, it is particularly desirable that thestructural unit (a0) includes at least one member selected from thegroup consisting of structural units represented by general formulas(a0-1) to (a0-3) shown below.

wherein R represents a hydrogen atom, an alkyl group, a halogen atom ora halogenated alkyl group; R²¹ represents an aliphatic cyclic grouphaving a valency of (e+1); R²² and R²³ each independently represents ahydrogen atom or a monovalent aliphatic cyclic group, with the provisothat at least one of R²² and R²³ represents an aliphatic cyclic group;a, d and f each independently represents an integer of 0 to 5; b and ceach independently represents an integer of 1 to 5; and e represents 2or 3.

The structural unit represented by general formula (a0-1) (hereafter,referred to as “structural unit (a0-1)”) is a structural unit whichcontains a norbornyl group having one specific fluorinated hydroxyalkylgroup [—(CH₂)_(a)—C(C_(b)F_(2b+1))(C_(c)F_(2c+1))—OH]. By including thestructural unit (a0-1), the effects of the present invention are furtherimproved.

In general formula (a0-1), as R, the same as those exemplified above forR in formula (a) can be mentioned.

In general formula (a0-1), R, is preferably a hydrogen atom or an alkylgroup, more preferably a hydrogen atom or a methyl group, and mostpreferably a hydrogen atom.

a is an integer of 1 to 5, preferably an integer of 1 to 3, and mostpreferably 1.

b and c each independently represents an integer of 1 to 5, preferably 1to 3, and most preferably 1.

The structural unit (a0-1) preferably has a 2-norbornyl group in which—(CH₂)_(a)—C(C_(b)F_(2b+1))(C_(c)F_(2c+1))—OH is bonded to the 5th or6th position of the norbornyl group. In terms of effects of the presentinvention, ease in synthesis and achieving high etching resistance, itis particularly desirable that R be a hydrogen atom or a methyl group,and all of a, b, and c be 1.

The structural unit represented by general formula (a0-2) (hereafter,referred to as “structural unit (a0-2)”) is a structural unit whichcontains an aliphatic cyclic group having two or three—(CH₂)_(d)—C(C_(b)F_(2b+1))(C_(c)F_(2c+1))—OH. By including thestructural unit (a0-2), the solubility in an alkali developing solutionis enhanced, and the effects of the present invention are furtherimproved.

In general formula (a0-2), R is the same as R in general formula (a0-1).In general formula (a0-2), R is preferably a hydrogen atom or an alkylgroup, more preferably a hydrogen atom or a methyl group, and mostpreferably a methyl group.

b and c are the same as b and c in formula (a0-1) above.

d is an integer of 0 to 5, preferably 0 or 1, and most preferably 0.

e is 2 or 3, and most preferably 2.

R²¹ represents an aliphatic cyclic group having a valency of (e+1). Theterm “aliphatic cyclic group having a valency of (e+1)” refers to analiphatic cyclic group in which (e+1) hydrogen atoms bonded to thecarbon atoms constituting the ring skeleton of the aliphatic cyclicgroup have been removed.

As the aliphatic cyclic group for R²¹, the same as those exemplifiedabove for the “aliphatic cyclic groups” can be mentioned. The aliphaticcyclic group for R²¹ may be monocyclic or polycyclic, although amonocyclic group is particularly desirable as it becomes superior in theeffects of the present invention.

R²¹ preferably has 3 to 20 carbon atoms, and more preferably 4 to 15carbon atoms. Specific examples include groups in which (e+1) hydrogenatoms have been removed from cyclopentane, cyclohexane, adamantane,norbornane, isobornane, tricyclodecane and tetracyclododecane. In thepresent invention, it is particularly desirable that R²¹ be a group inwhich (e+1) hydrogen atoms have been removed from cyclohexane.

The structural unit represented by general formula (a0-3) (hereafter,referred to as “structural unit (a0-3)”) is a structural unit having amethyl group in which the hydrogen atoms have been substituted with one—(CH₂)_(f)—C(C_(b)F_(2b+1))(C_(c)F_(2c+1))—OH and one or two aliphaticcyclic groups. By including the structural unit (a0-3), the effects ofthe present invention are further improved.

In general formula (a0-3), R is the same as R in general formula (a0-1).In general formula (a0-3), R is preferably a hydrogen atom or an alkylgroup, more preferably a hydrogen atom or a methyl group, and mostpreferably a methyl group.

b and c are the same as b and c in formula (a0-1) above.

f is preferably an integer of 1 to 5, more preferably 1 to 3, and mostpreferably 1.

R²² and R²³ each independently represents a hydrogen atom or amonovalent aliphatic cyclic group, with the proviso that at least one ofR²² and R²³ represents an aliphatic cyclic group. As the aliphaticcyclic group for R²² and R²³, the same as those exemplified above forthe “aliphatic cyclic groups” can be mentioned. The aliphatic cyclicgroup for R²¹ may be monocyclic or polycyclic, although a polycyclicgroup is particularly desirable as it becomes superior in the effects ofthe present invention.

R²² and R²³ preferably have 5 to 15 carbon atoms, and more preferably 6to 12 carbon atoms. Specifically, groups in which one or more hydrogenatoms have been removed from adamantane, norbornane, tricyclodecane,tetracyclododecane are preferable, and groups in which one or morehydrogen atoms have been removed from norbornane are particularlydesirable.

In the present invention, it is particularly desirable that either oneof R²² and R²³ be a hydrogen atom, and the other be an aliphatic cyclicgroup.

As the structural unit (a0), one type of structural unit may be used, ortwo or more types may be used in combination.

In the resin (A1), the amount of the structural unit (a0) based on thecombined total of all structural units constituting the resin (A1) ispreferably 5 to 80 mol %, more preferably 5 to 70 mol %, and mostpreferably 10 to 60 mol %. By making the amount of the structural unit(a0) at least as large as the lower limit of the above-mentioned range,the effects of including the structural unit (a0) can be satisfactorilyachieved. On the other hand, by making the amount of the structural unit(a0) no more than the upper limit of the above-mentioned range, a goodbalance can be achieved with the other structural units.

Structural Unit (a1)

When the resist composition for immersion exposure according to thepresent invention is a positive resist composition, it is preferablethat the resin (A1) have a structural unit (a1) derived from an acrylateester having an acid dissociable, dissolution inhibiting group.

As the acid dissociable, dissolution inhibiting group within thestructural unit (a1), any of the groups that have been proposed as aciddissociable, dissolution inhibiting groups for the base resins ofchemically amplified resists can be used, provided the group has analkali dissolution-inhibiting effect that renders the entire resin (A1)alkali-insoluble prior to exposure, and then following dissociation,causes the entire resin (A1) to change to an alkali-soluble state.Generally, groups that form either a cyclic or linear tertiary alkylester, or a cyclic or linear alkoxyalkyl ester with the carboxyl groupof the (meth)acrylate ester are the most widely known. In the presentdescription, the term “(meth)acrylate ester” is a generic term thatincludes either or both of the acrylate ester having a hydrogen atombonded to the α-position and the methacrylate ester having a methylgroup bonded to the α-position.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of the carboxyl group with alinear or cyclic tertiary alkyl group, and the tertiary carbon atomwithin the linear or cyclic tertiary alkyl group is bonded to the oxygenatom at the terminal of the carbonyloxy group (—C(O)—O—). In thistertiary alkyl ester, the action of acid causes cleavage of the bondbetween the oxygen atom and the tertiary carbon atom.

The linear or cyclic alkyl group may have a substituent. The linear orcyclic alkyl group preferably has 4 to 15 carbon atoms, and morepreferably 4 to 12 carbon atoms.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith the carboxyl group are referred to as “tertiary alkyl ester-typeacid dissociable, dissolution inhibiting groups”.

Furthermore, a cyclic or linear alkoxyalkyl ester describes a structurein which an ester is formed by substituting the hydrogen atom of thecarboxyl group with an alkoxyalkyl group, and the alkoxyalkyl group isbonded to the oxygen atom at the terminal of the carbonyloxy group(—C(O)—O—). In this alkoxyalkyl ester, the action of acid causescleavage of the bond between the oxygen atom and the alkoxyalkyl group.The alkoxyalkyl group preferably has 4 to 15 carbon atoms, morepreferably 4 to 12 carbon atoms.

As the structural unit (a1), it is preferable to use at least onestructural unit selected from the group consisting of structural unitsrepresented by a general formula (a1-0-1) shown below and structuralunits represented by a general formula (a1-0-2) shown below.

wherein, R represents a hydrogen atom, halogen atom, lower alkyl group,or halogenated lower alkyl group; and X¹ represents an acid dissociable,dissolution inhibiting group.

wherein, R represents a hydrogen atom, halogen atom, lower alkyl group,or halogenated lower alkyl group; X² represents an acid dissociable,dissolution inhibiting group; and Y² represents an alkylene group or analiphatic cyclic group.

In general formula (a1-0-1) shown above, the halogen atom, lower alkylgroup and halogenated lower alkyl group for R are the same as thehalogen atom, lower alkyl group or halogenated lower alkyl group whichcan be bonded to the α-position of the aforementioned acrylate ester.

There are no particular limitations on the group X¹, provided itfunctions as an acid dissociable, dissolution inhibiting group, andsuitable examples include an alkoxyalkyl group or a tertiary alkylester-type acid-dissociable, dissolution-inhibiting group, although atertiary alkyl ester-type acid dissociable, dissolution inhibiting groupis preferable. Examples of suitable tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups include aliphatic branchedacid dissociable, dissolution inhibiting groups and acid dissociable,dissolution inhibiting groups that contain an aliphatic cyclic group.

The “aliphatic cyclic group” within the structural unit (a1) may or maynot have a substituent.

Examples of suitable substituent groups include lower alkyl groups of 1to 5 carbon atoms, a fluorine atom, fluorinated lower alkyl groups of 1to 5 carbon atoms, and an oxygen atom (═O).

The basic ring structure of the “aliphatic cyclic group” excludingsubstituent groups is not limited to groups consisting of carbon andhydrogen (hydrocarbon groups), although a hydrocarbon group ispreferable. Furthermore, the “hydrocarbon group” may be either saturatedor unsaturated, but is preferably saturated. The aliphatic cyclic groupis preferably a polycyclic group.

Specific examples of this type of aliphatic cyclic group include groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as a monocycloalkane, bicycloalkane, tricycloalkaneor tetracycloalkane which may or may not be substituted with a loweralkyl group, a fluorine atom or a fluoroalkyl group. Specific examplesof suitable groups include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane, or a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

Specific examples of suitable aliphatic branched acid dissociable,dissolution inhibiting groups include a tert-butyl group and a tert-amylgroup.

Furthermore, examples of acid dissociable, dissolution inhibiting groupsthat contain an aliphatic cyclic group include groups that contain atertiary carbon atom within the ring skeleton of a cycloalkyl group, andspecific examples include a 2-methyl-2-adamantyl group or2-ethyl-2-adamantyl group. Other possible groups include those thatcontain an aliphatic cyclic group such as an adamantyl group, and abranched alkylene group that contains a tertiary carbon atom and isbonded to the aliphatic cyclic group, such as the group shown within thestructural unit represented by a general formula shown below.

wherein, R is as defined above, and R¹⁵ and R¹⁶ represent alkyl groups(which may be either linear or branched groups, and preferably have 1 to5 carbon atoms).

Furthermore, the above alkoxyalkyl groups are preferably groupsrepresented by general formula (p1) shown below.

wherein, R¹⁷ and R¹⁸ each independently represents a linear or branchedalkyl group or a hydrogen atom, and R¹⁹ represents a linear, branched orcyclic alkyl group. Furthermore, R¹⁷ and R¹⁹ may be bonded together attheir respective terminals to form a ring

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic group which preferably has 1to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched group, it preferably has 1 to 5carbon atoms, and is preferably a methyl group or an ethyl group, and amethyl group is most preferable.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cyclic group, groups in which one ormore hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be exemplified. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom monocycloalkanes such as cyclopentane and cyclohexane, and groupsin which one or more hydrogen atoms have been removed frompolycycloalkanes such as adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Of these, a group in which one ormore hydrogen atoms have been removed from adamantane is preferable.

Furthermore, in the above formula, R¹⁷ and R¹⁹ may each independentlyrepresent an alkylene group of 1 to 5 carbon atoms, wherein the terminalof R¹⁹ and the terminal of R¹⁷ are bonded together.

In such cases, a cyclic group is formed of the groups R¹⁷ and R¹⁹, theoxygen atom bonded to R¹⁹, and the carbon atom that is bonded to thisoxygen atom and the group R¹⁷. This type of cyclic group is preferably a4- to 7-membered ring, and more preferably 4- to 6-membered rings.Specific examples of these cyclic groups include a tetrahydropyranylgroup and a tetrahydrofuranyl group.

In the general formula (a1-0-2), R is as defined above. The group X² isas described for X¹ in the formula (a1-0-1).

Y² is an alkylene group of 1 to 4 carbon atoms or a divalent aliphaticcyclic group. As the aliphatic cyclic group, the same as thoseexemplified above in connection with the explanation of “aliphaticcyclic group” can be used, except that two hydrogen atoms have beenremoved therefrom.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

wherein X′ represents a tertiary alkyl ester-type acid dissociable,dissolution inhibiting group; Y represents a lower alkyl group of 1 to 5carbon atoms or an aliphatic cyclic group; n represents an integer of 0to 3; m represents 0 or 1; R is as defined above; and R¹, and R², eachindependently represents a hydrogen atom or a lower alkyl group of 1 to5 carbon atoms.

It is preferable that at least one of R¹′ and R²′ represent a hydrogenatom, and it is more preferable that both of R¹′ and R²′ represent ahydrogen atom. n is preferably 0 or 1.

Examples of the tertiary alkyl ester-type acid dissociable, dissolutioninhibiting group for X′ are the same as the tertiary alkyl ester-typeacid dissociable, dissolution inhibiting groups exemplified above forX¹.

Examples of the aliphatic cyclic group for Y are the same as thoseexemplified above in connection with the explanation of “aliphaticcyclic group”.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

As the structural unit (a1), either one type of structural unit may beused alone, or a combination of two or more different structural unitsmay be used.

Among these, structural units represented by general formula (a1-1) arepreferable. More specifically, at least one structural unit selectedfrom the group consisting of structural units represented by formulas(a1-1-1) to (a1-1-6) and (a1-1-35) to (a1-1-41) is more preferable.

Further, as the structural unit (a1), structural units represented bygeneral formula (a1-1-01) shown below which includes the structuralunits represented by formulas (a1-1-1) to (a1-1-4), and structural unitsrepresented by general formula (a1-1-02) shown below which includes thestructural units represented by formulas (a1-1-35) to (a1-1-41) arepreferable.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; and R¹¹ represents a loweralkyl group.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; R¹² represents a lower alkylgroup; and h represents an integer of 1 to 3.

In general formula (a1-1-01), R is as defined above. The lower alkylgroup for R¹¹ is the same as the lower alkyl group for R above, and ispreferably a methyl group or an ethyl group.

In general formula (a1-1-02), R is as defined above. The lower alkylgroup for R¹² is the same as the lower alkyl group for R above, and ispreferably a methyl group or an ethyl group, and most preferably anethyl group. h is preferably 1 or 2, and most preferably 2.

Further, as examples of structural units preferably used, structuralunits (a0) in which the hydrogen atom of the hydroxyl group of thefluorinated hydroxyalkyl group is substituted with an acid dissociable,dissolution inhibiting group can be mentioned. Specific examples includestructural units represented by general formulas (a1-5) to (a1-7) shownbelow. Among these, structural units represented by general formula(a1-6) are preferable.

In general formulas above, R, a, b, c, d, e and f are respectively thesame as R, a, b, c, d, e and f in general formulas (a0-1) to (a0-3)above.

In general formulas above, X³ is the same as X¹ in general formula(a1-0-1) above. As X³, an alkoxyalkyl group is preferable, a grouprepresented by general formula (p1) above is more preferable, and amethoxymethyl group is particularly desirable.

In the resin (A1), the amount of the structural unit (a1) based on thecombined total of all structural units constituting the resin (A1) ispreferably 10 to 80 mol %, more preferably 20 to 70 mol %, and stillmore preferably 25 to 60 mol %. By making the amount of the structuralunit (a1) at least as large as the lower limit of the above-mentionedrange, a pattern can be easily formed using a resist compositionprepared from the resin (A1). On the other hand, by making the amount ofthe structural unit (a1) no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

Structural Unit (a2)

The resin (A1) preferably has a structural unit (a2) derived from anacrylate ester having a lactone-containing cyclic group, as well as thestructural unit (a1).

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the resin (A1) is used for forming a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate,increasing the hydrophilicity, and enhancing the affinity for adeveloping solution.

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include groupsin which one hydrogen atom has been removed from γ-butyrolactone.Specific examples of lactone-containing polycyclic groups include groupsin which one hydrogen atom has been removed from a lactonering-containing bicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; R′ represents a hydrogen atom,a lower alkyl group or an alkoxy group of 1 to 5 carbon atoms; and mrepresents 0 or 1.

In general formulas (a2-1) to (a2-5), R is the same as R in thestructural unit (a1).

The lower alkyl group for R′ is the same as the lower alkyl group for Rin the structural unit (a1).

In the structural units represented by general formulas (a2-1) to(a2-5), in consideration of industrial availability, R′ is preferably ahydrogen atom.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) above are shown below.

Of these, at least one structural unit selected from the groupconsisting of formulas (a2-1) to (a2-5) is preferable, and at least onestructural unit selected from the group consisting of formulas (a2-1) to(a2-3) is more preferable. Specifically, it is preferable to use atleast one structural unit selected from the group consisting of formulas(a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2), (a2-3-1), (a2-3-2), (a2-3-9) and(a2-3-10).

In the resin (A1), as the structural unit (a2), one type of structuralunit may be used, or two or more types may be used in combination.

In the resin (A1), the amount of the structural unit (a2) based on thecombined total of all structural units constituting the resin (A1) ispreferably 5 to 70 mol %, more preferably 10 to 60 mol %, and still morepreferably 15 to 60 mol %. By making the amount of the structural unit(a2) at least as large as the lower limit of the above-mentioned range,the effect of using the structural unit (a2) can be satisfactorilyachieved. On the other hand, by making the amount of the structural unit(a2) no more than the upper limit of the above-mentioned range, a goodbalance can be achieved with the other structural units.

Structural Unit (a3)

The resin (A1) preferably has a structural unit (a3) derived from anacrylate ester having a polar group-containing aliphatic hydrocarbongroup (excluding structural units classified as structural unit (a0)),as well as the structural unit (a1) and the structural unit (a2). Byincluding the structural unit (a3), the hydrophilicity of the resin (A1)is improved, and hence, the affinity of the resin (A1) for a developingsolution is improved. As a result, the alkali solubility of the exposedportions improves, which contributes to favorable improvements in theresolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which some of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and polycyclic aliphatic hydrocarbon groups (polycyclic groups). Thesepolycyclic groups can be selected appropriately from the multitude ofgroups that have been proposed for the resins of resist compositionsdesigned for use with ArF excimer lasers.

Of the various possibilities, structural units derived from acrylateesters having an aliphatic polycyclic group that contains a hydroxylgroup, cyano group, carboxyl group or a hydroxyalkyl group in which someof the hydrogen atoms of the alkyl group have been substituted withfluorine atoms are particularly desirable. Examples of suitablepolycyclic groups include groups in which one or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane ortetracycloalkane or the like. Specific examples include groups in whichone or more hydrogen atoms have been removed from a polycycloalkane suchas adamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, groups in whichtwo or more hydrogen atoms have been removed from norbornane, and groupsin which two or more hydrogen atoms have been removed fromtetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit represented by general formula (a) above in which X is a(linear or branched) chain hydroxyalkyl group.

On the other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1) and (a3-2) shown beloware preferable.

wherein R is as defined above; j is an integer of 1 to 3; and k is aninteger of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is particularlydesirable that the hydroxyl group be bonded to the 3rd position of theadamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbonyl group.

As the structural unit (a3), one type of structural unit may be used, ortwo or more types may be used in combination.

In the resin (A1), the amount of structural unit (a3) based on thecombined total of all structural units constituting the resin (A1) ispreferably 5 to 50 mol %, more preferably 5 to 40 mol %, and still morepreferably 5 to 25 mol %.

Structural Unit (a4)

The resin (A1) may further contain a structural unit (a4) which is otherthan the above-mentioned structural units (a0) to (a3), as long as theeffects of the present invention are not impaired.

As the structural unit (a4), any other structural unit which cannot beclassified as one of the above structural units (a0) to (a3) can be usedwithout any particular limitations, and any of the multitude ofconventional structural units used within resist resins for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

As the structural unit (a4), a structural unit derived from an acrylateester having a non-acid-dissociable aliphatic polycyclic group ispreferable. Examples of this polycyclic group include the same groups asthose described above in relation to the aforementioned structural unit(a1), and any of the multitude of conventional polycyclic groups usedwithin the resin component of resist compositions for ArF excimer lasersor KrF excimer lasers (and particularly for ArF excimer lasers) can beused.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecanyl group,adamantyl group, tetracyclododecanyl group, isobornyl group, andnorbornyl group is particularly desirable. These polycyclic groups mayhave at least one of the hydrogen atoms substituted with a linear orbranched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-5) shown below.

wherein R is as defined above.

When the structural unit (a4) is included in the resin (A1), the amountof the structural unit (a4) based on the combined total of all thestructural units that constitute the resin (A1) is typically within arange from 1 to 30 mol %, and preferably from 10 to 20 mol %.

In the present invention, the resin (A1) is preferably a copolymerincluding at least the structural units (a0) and (a1). Examples of sucha copolymer include a copolymer consisting of the structural units (a0)and (a1), a copolymer consisting of the structural units (a0), (a1) and(a2), and a copolymer consisting of the structural units (a0), (a1),(a2) and (a3).

In the present invention, as the resin (A1), copolymers including acombination of 2 to 4 structural units represented by formulas (A1-11)to (A1-15) shown below are particularly desirable.

In general formulas above, X³ is the same as X³ in general formula(a1-6) above.

In general formulas above, R, a, b, c, d, e and f are respectively thesame as R, a, b, c, d, e and f in general formulas (a0-1) to (a0-3)above.

R⁹ represents a lower alkyl group, and is the same as the lower alkylgroup for R. R⁹ is preferably a methyl group or an ethyl group, and ismost preferably an ethyl group.

The resin (A1) can be obtained, for example, by a conventional radicalpolymerization or the like of the monomers corresponding with each ofthe structural units, using a radical polymerization initiator such asazobisisobutyronitrile (AIBN).

Furthermore, in the resin (A1), by using a chain transfer agent such asHS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced at theterminals of the resin (A1). Such a copolymer having introduced ahydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in decreasingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the resin (A1) isnot particularly limited, but is preferably 2,000 to 30,000, morepreferably 2,000 to 10,000, and still more preferably 3,000 to 7,000. Bymaking the weight average molecular weight within the above-mentionedrange, the resin (A1) exhibits satisfactory dissolution rate can beachieved in an alkali developing solution, and becomes preferable interms of achieving high resolution. There is a tendency thatsatisfactory properties can be obtained when the molecular weight issmaller within the above-mentioned range.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 2.5.

In the present invention, it is necessary that the amount of the resin(A1) within the component (A) be within the range from 0.1 to 50% byweight. By making the amount of the resin (A1) 0.1% by weight or more,the resistance to an immersion medium becomes satisfactory. On the otherhand, by making the amount of the resin (A1) no more than 50% by weight,the balance with the resin (A2) becomes satisfactory, and satisfactorylithography properties can be achieved.

The amount of the resin (A1) within the component (A) is preferably from0.1 to 25% by weight, more preferably 0.1 to 20% by weight, and mostpreferably 0.1 to 10% by weight.

[Resin (A2)]

As the resin (A2), there is no particular limitation as long as it is aresin which has a structural unit (a′) derived from acrylic acid andcontains no fluorine atom, and one or more kinds of alkali-solubleresins or resins capable of becoming alkali-soluble, which haveconventionally been proposed as a chemically amplified photoresist canbe exemplified. When the former is used, the resist composition becomesa negative type, and when the latter is used, the composition becomes apositive type.

As the structural unit (a′), among the structural unit (a) mentionedabove in connection with the resin (A1), those which do not containfluorine atoms can be mentioned.

In the resin (A2), the amount of the structural unit (a′) based on thecombined total of all structural units constituting the resin (A2) ispreferably 50 to 100 mol %, and more preferably 70 to 100 mol %. It isparticularly desirable that the resin (A2) consist of the structuralunit (a′) derived from acrylic acid, as the effects of the presentinvention becomes excellent.

Here, the expression “consisting of the structural unit (a′)” means thatthe main chain of the resin (A2) is constituted from only the structuralunit (a′), and does not contain any other structural units.

Structural Unit (a′1)

When the resist composition for immersion exposure according to thepresent invention is a positive resist composition, it is preferablethat the resin (A2) have a structural unit (a′1) derived from anacrylate ester containing no fluorine atom and having an aciddissociable, dissolution inhibiting group.

As the structural unit (a′1), structural unit (a1) which contain nofluorine atoms can be used.

In the resin (A2), as the structural unit (a′1), one type of structuralunit may be used, or two or more types may be used in combination.

In the resin (A2), the amount of the structural unit (a′1) based on thecombined total of all structural units constituting the resin (A2) ispreferably 10 to 80 mol %, more preferably 20 to 70 mol %, and stillmore preferably 30 to 60 mol %. By making the amount of the structuralunit (a′1) at least as large as the lower limit of the above-mentionedrange, a pattern can be easily formed using a resist compositionprepared from the resin (A2). On the other hand, by making the amount ofthe structural unit (a′1) no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

Structural Unit (a′2)

The resin (A2) preferably has a structural unit (a′2) derived from anacrylate ester containing no fluorine atoms and having alactone-containing cyclic group, as well as the structural unit (a′1).

As the structural unit (a′2), structural unit (a2) which contain nofluorine atoms can be used.

In the resin (A2), as the structural unit (a′2), one type of structuralunit may be used, or two or more types may be used in combination.

In the resin (A2), the amount of the structural unit (a′2) based on thecombined total of all structural units constituting the resin (A2) ispreferably 5 to 70 mol %, more preferably 10 to 60 mol %, and still morepreferably 20 to 50 mol %. By making the amount of the structural unit(a′2) at least as large as the lower limit of the above-mentioned range,the effect of using the structural unit (a′2) can be satisfactorilyachieved. On the other hand, by making the amount of the structural unit(a′2) no more than the upper limit of the above-mentioned range, a goodbalance can be achieved with the other structural units.

Structural Unit (a′3)

The resin (A2) preferably has a structural unit (a′3) derived from anacrylate ester containing no fluorine atoms and having a polargroup-containing aliphatic hydrocarbon group, as well as the structuralunit (a′1) and the structural unit (a′2).

As the structural unit (a′3), structural unit (a3) which contain nofluorine atoms can be used.

In the resin (A2), as the structural unit (a′3), one type of structuralunit may be used, or two or more types may be used in combination.

In the resin (A2), the amount of structural unit (a′3) based on thecombined total of all structural units constituting the resin (A2) ispreferably 5 to 50 mol %, more preferably 5 to 40 mol %, and still morepreferably 5 to 25 mol %.

Structural Unit (a′4)

The resin (A2) may further contain a structural unit (a′4) which isother than the above-mentioned structural units (a′1) to (a′3), as longas the effects of the present invention are not impaired.

As the structural unit (a′4), any other structural unit which containsno fluorine atoms and cannot be classified as one of the abovestructural units (a′1) to (a′3) can be used without any particularlimitations, and any of the multitude of conventional structural unitsused within resist resins for ArF excimer lasers or KrF excimer lasers(and particularly for ArF excimer lasers) can be used.

As the structural unit (a′4), structural unit (a4) which contain nofluorine atoms can be used.

In the resin (A2), as the structural unit (a′4), one type of structuralunit may be used, or two or more types may be used in combination.

When the structural unit (a′4) is included in the resin (A2), the amountof the structural unit (a′4) based on the combined total of all thestructural units that constitute the resin (A2) is typically within arange from 1 to 30 mol %, and preferably from 10 to 20 mol %.

In the present invention, the resin (A2) is preferably a copolymerincluding at least the structural units (a′1), (a′2) and (a′3). Examplesof such a copolymer include a copolymer consisting of the structuralunits (a′1), (a′2) and (a′3), and a copolymer consisting of thestructural units (a′1), (a′2), (a′3) and (a′4).

In the present invention, as the resin (A2), a copolymer including acombination of 3 structural units represented by formula (A2-11) shownbelow is particularly desirable.

wherein R″ represents a hydrogen atom, a halogen atom other than afluorine atom, a lower alkyl group or a lower alkyl group in which thehydrogen atoms have been substituted with halogen atoms other thanfluorine atoms (halogenated lower alkyl group); and R¹⁰ represents alower alkyl group.

In formula (A2-11) above, the lower alkyl group for R″ is the same asthe lower alkyl group for R. As R″, a hydrogen atom or a lower alkylgroup is preferable, and a hydrogen atom or a methyl group is morepreferable.

The lower alkyl group for R¹⁰ is the same as the lower alkyl group forR″. As R¹⁰, a methyl group or an ethyl group is preferable, and a methylgroup is particularly desirable.

The resin (A2) can be obtained, for example, by a conventional radicalpolymerization or the like of the monomers corresponding with each ofthe structural units, using a radical polymerization initiator such asazobisisobutyronitrile (AIBN).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the resin (A2) isnot particularly limited, but is preferably 2,000 to 50,000, morepreferably 3,000 to 30,000, and most preferably 5,000 to 20,000. Bymaking the weight average molecular weight no more than the upper limitof the above-mentioned range, the resin (A2) exhibits satisfactorysolubility in a resist solvent when used as a resist. On the other hand,by making the weight average molecular weight at least as large as thelower limit of the above-mentioned range, dry etching resistance andcross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

In the component (A), as the resin (A2), one type of resin may be used,or two or more types may be used in combination.

The amount of the resin (A2) within the component (A) is preferablywithin the range of 50 to 99.9% by weight, more preferably from 80 to99.9% by weight, and still more preferably 90 to 99.9% by weight. Bymaking the amount of the resin (A2) 50% by weight or more, satisfactorylithography properties can be achieved. On the other hand, by making theamount of the resin (A2) no more than 99.9% by weight, the balance withthe resin (A1) becomes satisfactory, and the resistance to an immersionmedium becomes satisfactory.

<Component (B)>

As the component (B), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used. Examples of these acid generators arenumerous, and include onium salt-based acid generators such as iodoniumsalts and sulfonium salts; oxime sulfonate-based acid generators;diazomethane-based acid generators such as bisalkyl or bisaryl sulfonyldiazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate-based acid generators; iminosulfonate-based acidgenerators; and disulfone-based acid generators.

Examples of onium salt-based acid generators include compoundsrepresented by general formula (b-0) shown below.

wherein R⁵¹ represents a linear, branched or cyclic alkyl group, or alinear, branched or cyclic fluorinated alkyl group; R⁵² represents ahydrogen atom, a hydroxyl group, a halogen atom, a linear or branchedalkyl group, a linear or branched halogenated alkyl group, or a linearor branched alkoxy group; R⁵³ represents an aryl group which may have asubstituent; and u″ represents an integer of 1 to 3.

In general formula (b-0), R⁵¹ represents a linear, branched or cyclicalkyl group, or a linear, branched or cyclic fluorinated alkyl group.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group preferably has 4 to 12 carbon atoms, morepreferably 5 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

The linear or branched fluorinated alkyl group preferably has 1 to 10carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1to 4 carbon atoms. The cyclic fluorinated alkyl group preferably has 4to 12 carbon atoms, more preferably 5 to 10 carbon atoms, and mostpreferably 6 to 10 carbon atoms. The fluorination ratio of thefluorinated alkyl group (percentage of the number of fluorine atomssubstituting the hydrogen atoms within the alkyl group, based on thetotal number of hydrogen atoms within the alkyl group prior tofluorination) is preferably from 10 to 100%, more preferably from 50 to100%, and it is particularly desirable that all of the hydrogen atomsare substituted with fluorine atoms, as the acid strength increases.

R⁵¹ is most preferably a linear alkyl group or fluorinated alkyl group.

R⁵² represents a hydrogen atom, a hydroxyl group, a halogen atom, alinear or branched alkyl group, a linear or branched halogenated alkylgroup, or a linear or branched alkoxy group.

Examples of the halogen atom for R⁵² include a fluorine atom, a bromineatom, a chlorine atom and an iodine atom, and a fluorine atom ispreferable.

The alkyl group for R⁵² is linear or branched, and preferably has 1 to 5carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably 1to 3 carbon atoms.

The halogenated alkyl group for R⁵² is a group in which some or all ofthe hydrogen atoms of the alkyl group have been substituted with halogenatoms. As the alkyl group of the halogenated alkyl group, the same asthe alkyl group for R⁵² may be exemplified. As the halogen atoms forsubstituting the hydrogen atoms of the alkyl group, the same as thehalogen atom for R⁵² may be exemplified. In the halogenated alkyl group,it is preferable that 50 to 100% of the hydrogen atoms of the alkylgroup be substituted with halogen atoms, and it is more preferable thatall of the hydrogen atoms are substituted with halogen atoms.

The alkoxy group for R⁵² is linear or branched, and preferably has 1 to5 carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably1 to 3 carbon atoms.

Among these, as R⁵², a hydrogen atom is particularly desirable.

R⁵³ represents an aryl group which may have a substituent, preferably anaryl group of 6 to 20 carbon atoms, and examples of the basic ringexcluding the substituent include a naphthyl group, a phenyl group andan anthracenyl group. In terms of the effects of the present inventionand absorption of exposure ray such as ArF excimer laser, a phenyl groupis preferable.

Examples of the substituent include a hydroxyl group and a lower alkylgroup (linear or branched, and preferably has no more than 5 carbonatoms, and a methyl group is particularly desirable).

As the aryl group for R⁵³, those which do not have a substituent arepreferable.

u″ is an integer of 1 to 3, preferably 2 or 3, and it is particularlydesirable that u″ be 3.

As preferable examples of acid generators represented by general formula(b-0), the following can be exemplified (acid generator group (b-0-1)).

Examples of onium salt-based acid generators other than thoserepresented by general formula (b-0) include compounds represented bygeneral formula (b-1) or (b-2) shown below.

wherein R¹″ to R³″, R⁵″ and R⁶″ each independently represents an arylgroup or alkyl group; and R⁴″ represents a linear, branched or cyclicalkyl group or fluorinated alkyl group, with the proviso that at leastone of R¹″ to R³″ represents an aryl group, and at least one of R⁵″ andR⁶″ represents an aryl group.

In formula (b-1), R¹″ to R³″ each independently represents an aryl groupor an alkyl group. Among R¹″ to R³″, at least one group represents anaryl group. Among R¹″ to R³″, two or more groups are preferably arylgroups, and it is particularly desirable that all of R¹″ to R³″ be arylgroups.

The aryl group for R¹″ to R³″ is not specifically limited. For example,an aryl group having 6 to 20 carbon atoms may be used in which some orall of the hydrogen atoms of the aryl group may or may not besubstituted with alkyl groups, alkoxy groups or halogen atoms. The arylgroup is preferably an aryl group having 6 to 10 carbon atoms because itcan be synthesized at a low cost. Specific examples thereof include aphenyl group and naphthyl group.

The alkyl group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkyl group having 1 to 5 carbon atoms,and most preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkoxy group having 1 to 5 carbon atoms,and most preferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may besubstituted, is preferably a fluorine atom.

The alkyl group for R¹″ to R³″ is not specifically limited and includes,for example, a linear, branched or cyclic alkyl group having 1 to 10carbon atoms. In terms of achieving excellent resolution, the alkylgroup preferably has 1 to 5 carbon atoms. Specific examples thereofinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, an n-pentyl group, acyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, anda decanyl group, and a methyl group is most preferable because it isexcellent in resolution and can be synthesized at a low cost.

It is particularly desirable that each of R¹″ to R³″ be a phenyl groupor a naphthyl group.

R⁴″ represents a linear, branched or cyclic alkyl group or fluorinatedalkyl group.

The linear alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.

The cyclic alkyl group is preferably a cyclic group, as described forR¹″, having 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms,and most preferably 6 to 10 carbon atoms.

The fluorinated alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.

Further, the fluorination ratio of the fluorinated alkyl group (ratio offluorine atoms within the alkyl group) is preferably from 10 to 100%,more preferably from 50 to 100%, and it is particularly desirable thatall hydrogen atoms are substituted with fluorine atoms because the acidstrength increases.

R⁴″ is most preferably a linear or cyclic alkyl group or fluorinatedalkyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represents an arylgroup or alkyl group. At least one of R⁵″ and R⁶″ represents an arylgroup. It is preferable that both of R⁵″ and R⁶″ represent an arylgroup.

As the aryl group for R⁵″ and R⁶″, the same as the aryl groups for R¹″to R³″ can be exemplified.

As the alkyl group for R⁵″ and R⁶″, the same as the alkyl groups for R¹″to R³″ can be exemplified.

It is particularly desirable that both of R⁵″ and R⁶″ represent a phenylgroup.

As R⁴″ in formula (b-2), the same as those mentioned above for R⁴″ informula (b-1) can be exemplified.

Specific examples of suitable onium salt-based acid generatorsrepresented by formula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate,bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate, triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate,diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate; anddi(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate. It is alsopossible to use onium salts in which the anion moiety of these oniumsalts are replaced by methanesulfonate, n-propanesulfonate,n-butanesulfonate, or n-octanesulfonate.

Further, acid generators in which the anion moiety in general formula(b-1) or (b-2) is replaced with an anion moiety represented by generalformula (b-3) or (b-4) shown below (the cation moiety is the same as(b-1) or (b-2)) may be used.

wherein X″ represents an alkylene group of 2 to 6 carbon atoms in whichat least one hydrogen atom has been substituted with a fluorine atom;and Y″ and Z″ each independently represents an alkyl group of 1 to 10carbon atoms in which at least one hydrogen atom has been substitutedwith a fluorine atom.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

Y″ and Z″ each independently represents a linear or branched alkyl groupin which at least one hydrogen atom has been substituted with a fluorineatom, and the alkyl group has 1 to 10 carbon atoms, preferably 1 to 7carbon atoms, and more preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group of X″ orthose of the alkyl group of Y″ and Z″ within the range of the number ofcarbon atoms, the better the solubility in a resist solvent.

Further, in the alkylene group of X″ or the alkyl group of Y″ and Z″, itis preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible, as the acid strength increases,and the transparency to high energy radiation of 200 nm or less orelectron beam is improved. The fluorination ratio of the alkylene groupor alkyl group is preferably from 70 to 100%, more preferably from 90 to100%, and it is particularly desirable that the alkylene group or alkylgroup be a perfluoroalkylene group or perfluoroalkyl group in which allhydrogen atoms are substituted with fluorine atoms.

In the present description, an oximesulfonate-based acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate-based acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

wherein R³¹ and R³² each independently represents an organic group.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The expression “having a substituent”means that some or all of the hydrogen atoms of the alkyl group or thearyl group are replaced with substituents.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which some of the hydrogen atoms aresubstituted with halogen atoms, and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is particularly desirable. In other words, the halogenatedalkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms, and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² are the same as those of the alkyl group andthe aryl group for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate-based acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

wherein R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

wherein R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As for the R³³, a halogenated alkyl group is preferable, and afluorinated alkyl group is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms of the alkyl group fluorinated, more preferably 70% ormore, and still more preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthracyl group, and a phenantryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. Thehalogenated alkyl group is preferably a fluorinated alkyl group.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, a fluorinated alkylgroup is more preferable, and a partially fluorinated alkyl group isparticularly desirable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms of the alkyl group fluorinated, more preferably 70% ormore, still more preferably 90% or more. A completely fluorinated alkylgroup in which 100% of the hydrogen atoms are substituted with fluorineatoms is particularly desirable.

In general formula (B-3), the alkyl group having no substituent and thehalogenated alkyl group for R³⁶ are the same as the alkyl group havingno substituent and the halogenated alkyl group for R³³.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate-based acid generatorsinclude α-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate-based acid generators disclosed in WO 2004/074242A2(Examples 1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following (compounds (B-4)) canbe exemplified.

Among the above-exemplified compounds, the following 4 compounds arepreferable.

Of the aforementioned diazomethane-based acid generators, specificexamples of suitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 11-035551,Japanese Unexamined Patent Application, First Publication No. Hei11-035552 and Japanese Unexamined Patent Application, First PublicationNo. Hei 11-035573 may be preferably used.

Furthermore, as poly(bis-sulfonyl)diazomethanes, those disclosed inJapanese Unexamined Patent Application, First Publication No. Hei11-322707, including 1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may beexemplified.

As the component (B), one type of acid generator may be used, or two ormore types may be used in combination.

In the present invention, as the component (B), it is preferable to usean onium salt having a fluorinated alkylsulfonic acid ion as the anionmoiety.

The amount of the component (B) within the resist composition forimmersion exposure according to the present invention is typically 0.5to 30 parts by weight, and preferably 1 to 10 parts by weight, relativeto 100 parts by weight of the component (A). When the amount of thecomponent (B) is within the above-mentioned range, formation of a resistpattern can be satisfactorily performed. Further, by virtue of theabove-mentioned range, a uniform solution can be obtained and thestorage stability becomes satisfactory.

<Optional Components>

In the resist composition for immersion exposure according to thepresent invention, for improving the resist pattern shape and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer, it is preferable to add anitrogen-containing organic compound (D) (hereafter referred to as thecomponent (D)) as an optional component.

A multitude of these components (D) have already been proposed, and anyof these known compounds may be used, although a cyclic amine, analiphatic amine, and particularly a secondary aliphatic amine ortertiary aliphatic amine is preferable.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines). Specific examples of these aliphatic aminesinclude monoalkylamines such as n-hexylamine, n-heptylamine,n-octylamine, n-nonylamine, and n-decylamine; dialkylamines such asdiethylamine, di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decanylamine, and tri-n-dodecylamine; andalkylalcoholamines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine.

Among these, alkylalcoholamines and trialkylamines are preferable, andalkylalcoholamines are particularly desirable. Among alkylalcoholamines,triethanolamine and triisopropanolamine are preferable.

Examples of the cyclic amine include a heterocyclic compound containinga nitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidineand piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

These compounds can be used either alone, or in combinations of two ormore different compounds.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

Furthermore, in the resist composition for immersion exposure accordingto the present invention, for preventing any deterioration insensitivity, and improving the resist pattern shape and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer, an organic carboxylic acid, or aphosphorus oxo acid or derivative thereof (E) (hereafter referred to asthe component (E)) can also be added as another optional component.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of suitable phosphorus oxo acids or derivatives thereof includephosphoric acid or derivatives thereof such as esters, includingphosphoric acid, di-n-butyl phosphate and diphenyl phosphate; phosphonicacid or derivatives thereof such as esters, including phosphonic acid,dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonic acid,diphenyl phosphonate, and dibenzyl phosphonate; and phosphinic acid orderivatives thereof such as esters, including phosphinic acid andphenylphosphinic acid.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

If desired, other miscible additives can also be added to the resistcomposition for immersion exposure according to the present invention.Examples of such miscible additives include additive resins forimproving the performance of the resist film, surfactants for improvingthe applicability, dissolution inhibitors, plasticizers, stabilizers,colorants, halation prevention agents, and dyes.

The resist composition for immersion exposure according to the presentinvention can be prepared by dissolving the materials for the resistcomposition in an organic solvent (hereafter, frequently referred to as“component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and any one or morekinds of organic solvents can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone, methyl-n-amyl ketonemethyl isoamyl ketone, and 2-heptanone; polyhydric alcohols andderivatives thereof, such as ethylene glycol, diethylene glycol,propylene glycol and dipropylene glycol; polyhydric alcohol derivativesincluding compounds having an ether bond, such as a monoalkylether(e.g., monomethylether, monoethylether, monopropylether ormonobutylether) or monophenylether of any of these polyhydric alcoholsor compounds having an ester bond; cyclic ethers such as dioxane; esterssuch as methyl lactate, ethyl lactate (EL), methyl acetate, ethylacetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; and aromatic organicsolvents such as anisole, ethylbenzylether, cresylmethylether,diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, amylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, propylene glycol monomethyl ether acetate (PGMEA),propylene glycol monomethyl ether (PGME) and EL are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably from 1:9 to 9:1, more preferably from 2:8 to 8:2.

More specifically, when EL is mixed as the polar solvent, the PGMEA:ELweight ratio is preferably from 1:9 to 9:1, and more preferably from 2:8to 8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME is preferably from 1:9 to 9:1, more preferably from 2:8 to8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the component (S) is used in an amount suchthat the solid content of the resist composition becomes within therange from 2 to 20% by weight, and preferably from 5 to 15% by weight.

Dissolving of the materials for a resist composition in the component(S) can be conducted by simply mixing and stirring each of the abovecomponents together using conventional methods, and where required, thecomposition may also be mixed and dispersed using a dispersion devicesuch as a dissolver, a homogenizer, or a triple roll mill. Furthermore,following mixing, the composition may also be filtered using a mesh or amembrane filter or the like.

By the resist composition for immersion exposure according to thepresent invention, both of excellent resistance to an immersion mediumand excellent lithography properties can be achieved. The reason forthis has not been elucidated yet, but is presumed that the properties ofthe resist film surface is changed by using a combination of the resin(A1) and resin (A2) as the component (A), and including the resin (A1)in an specific amount.

More specifically, the reason is presumed as follows. With respect to aresist film formed by using the resist composition for immersionexposure according to the present invention, the balance between thecontact angles to water such as the static contact angle (the contactangle as measured with respect to the resist film in a horizontalstate), the dynamic contact angle (the contact angle at which a waterdroplet starts to slide when the resist film is inclined, including thecontact angle at the front-end point of the water droplet in the slidingdirection (advancing angle) and the contact angle at the rear-end pointof the water droplet in the sliding direction (receding angle)) andsliding angle (the inclination angle of the resin film at which a waterdroplet starts to slide when the resist film is inclined) is differentfrom a resist composition in which only the resin (A2) is used as thecomponent (A). For example, the static contact angle (hereafter, in thepresent description, the static contact angle is simply referred to asthe contact angle) and the receding angle become large. On the otherhand, the sliding angle is not always affected by the addition of theresin (A1), and the sliding angle may become larger or smaller, or maynot change.

As described above, in an immersion exposure, the resist film comes intocontact with an immersion medium such as water. Therefore, it ispresumed that the elution of a substance from the resist is affected bythe properties of the resist film surface (e.g., hydrophilicity andhydrophobicity). In the present invention, it is presumed that theproperties of the resist film surface are changed by the use of thespecific component (A), and as a result, a resist film in which theelution of a substance is suppressed and which exhibits excellentlithography properties can be obtained.

As shown in FIG. 1, when a droplet 1 is placed on a plane 2 and theplane 2 is gradually inclined, the receding angle is the angle θ₁ formedbetween the upper end 1 a of the droplet 1 and the plane 2 as thedroplet 1 starts to move (slide) on the plane 2. The sliding angle isthe inclination angle θ₂ of the plane 2 as measured when the droplet 1starts to move (slide) on the plane 2.

In the present description, the contact angle is measured in thefollowing manner.

First, a resist composition solution is spin-coated onto a siliconesubstrate having a diameter of 6 inches, and then heated at atemperature of 90° C. for 90 seconds to form a resist film.

Thereafter, using FACE contact angle meter, model CA-X150 (product name;manufactured by Kyowa Interface Science Co., Ltd.), the resin film iscontacted with a microsyringe equipped on the contact angle meter(whereby 2 μL of pure water is droppped from the microsyringe), and thecontact angle is measured with respect to a formed droplet.

In the present description, the receding angle and the sliding angle canbe measured by forming a resist film in the same manner as describedabove, followed by measuring the angles using commercially availablemeasurement apparatuses such as AUTO SLIDING ANGLE: SA-30 DM(manufactured by Kyowa Interface Science Co. Ltd.), and AUTO DISPENSER:AD-31 (manufactured by Kyowa Interface Science Co. Ltd.).

With respect to the resist composition for immersion exposure accordingto the present invention, it is preferable that a resist film formed byusing the resist composition have a contact angle of 60 degrees or more,more preferably 65 degrees or more, and most preferably 60 to 90degrees. When the contact angle is 60 degrees or more, the effect ofsuppressing the elution of a substance during the immersion exposure isenhanced. The reason for this has not been elucidated yet, but it ispresumed that one of the main reasons is related to the hydrophobicityof the resist film. More specifically, it is presumed that since anaqueous substance such as water is used as the immersion medium, higherhydrophobicity has an influence on the swift removal of the immersionmedium from the surface of the resist film after the immersion exposure.On the other hand, when the contact angle is 90 degrees or less, theeffects of the invention can be satisfactorily achieved.

For the same reasons as described above, with respect to the resistcomposition for immersion exposure according to the present invention,it is preferable that a resist film formed by using the resistcomposition have a receding angle of 45 degrees or more, more preferably50 to 150 degrees, still more preferably 55 to 130 degrees, and mostpreferably 60 to 100 degrees.

The level of the contact angle and the receding angle can be adjusted bychanging the mixing ratio of the resin (A1) and the resin (A2) withinthe component (A), and the amount of the structural unit (a′3). Forexample, by making the amount of the resin (A1) within the component (A)1% by weight or more, the receding angle becomes significantly large ascompared to the case where the resin (A2) is used alone.

As described above, in the present invention, elution of a substanceinto the immersion medium can be suppressed. As a result, degenerationof the resist film and change in refractive index of the immersionmedium can also be suppressed. Further, as a result of suppression ofchange in refractive index of the immersion medium and the like, variouslithography properties such as undulation and LER of the pattern andshape of the resist pattern becomes satisfactory, and the level ofcontamination of the lens within the exposure apparatus can be lowered.Therefore, there is no need for protection against these disadvantages,and hence, the present invention can contribute to simplifying theprocess and the exposure apparatus.

Next, the method of forming a resist pattern according to the presentinvention will be described.

The method of forming a resist pattern according to the presentinvention includes applying a resist composition for immersion exposureaccording to the present invention to a substrate to form a resist filmon the substrate; subjecting the resist film to immersion exposure; anddeveloping the resist film to form a resist pattern.

A preferable example of the method of forming a resist pattern accordingto the present invention will be described.

First, a resist composition for immersion exposure according to thepresent invention is applied to the surface of a substrate such as asilicon wafer using a spinner or the like, and a prebake (PAB treatment)is performed, to thereby form a resist film.

An organic or inorganic anti-reflection film may be optionally providedbetween the substrate and the applied layer of the resist composition toform a double-layer laminate.

Alternatively, a double-layer laminate in which an organicanti-reflective film is provided on top of the resist film can beformed, or a triple-layer laminate further including an additionalbottom layer anti-reflection film can be formed.

The anti-reflection film provided on top of the resist film ispreferably soluble in an alkali developing solution.

The steps up until this point can be conducted by using conventionaltechniques. The operating conditions and the like are appropriatelyselected depending on the formulation and the characteristics of theresist composition for immersion exposure being used.

Subsequently, the obtained resist film is subjected to selectiveimmersion exposure (liquid immersion lithography) through a desired maskpattern. At this time, the region between the resist film and the lensat the lowermost point of the exposure apparatus is pre-filled with asolvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

There are no particular limitations on the wavelength used for theexposure, and an ArF excimer laser, KrF excimer laser or F₂ laser or thelike can be used. The resist composition according to the presentinvention is effective for KrF or ArF excimer lasers, and isparticularly effective for ArF excimer lasers.

As described above, in a formation method of the present invention,during exposure, the region between the resist film and the lens at thelowermost point of the exposure apparatus is filled with an immersionmedium, and exposure (immersion exposure) is conducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist composition being used. The refractive index of the immersionmedium is not particularly limited as long at it satisfies theabove-mentioned requirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist composition being used include water,fluorine-based inert liquids, and silicon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

A resist composition for immersion exposure according to the presentinvention is particularly resistant to any adverse effects caused bywater, and because the resulting sensitivity and shape of the resistpattern profile are excellent, water is preferably used as the immersionmedium which exhibits a refractive index that is larger than therefractive index of air. Furthermore, water is also preferred in termsof cost, safety, environmental friendliness, and versatility.

Subsequently, following completion of the immersion exposure step, postexposure baking (PEB) is conducted, and then a developing treatment isperformed using an alkali developing liquid formed from an aqueousalkali solution. Thereafter, water rinse is preferably conducted withpure water. This water rinse is conducted by dripping or spraying wateronto the surface of the substrate while rotating the substrate, andwashes away the developing solution and those portions of the resistcomposition for immersion exposure that have been dissolved by thedeveloping solution. By conducting a subsequent drying treatment, aresist pattern is obtained in which the resist film (coating of theresist composition for immersion exposure) has been patterned into ashape corresponding to the mask pattern.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

In the following examples and comparative examples, the resins used weresynthesized from monomers (1) to (7) described below. Specifically, amonomer having the composition shown in Table 1 was dissolved intetrahydrofuran (THF), and a radical polymerization initiator V-601(Wako Pure Chemical Industries, Ltd.) was added thereto, to therebyobtain a mixed solution. The obtained mixed solution was dropwise addedto THF in a separate container over 6 hours to effect a polymerizationreaction, thereby obtaining a resin.

With respect to the obtained resin, GPC measurement was conducted, andthe weight average molecular weight (Mw) and dispersity thereof weredetermined. The results are shown in Table 1.

TABLE 1 (1) (2) (3) (4) (5) (6) (7) Mw Mw/Mn (A)-1 30 50 20 10000 1.7(A)-2′ 100 12000 1.3 (A)-3 50 50 13600 1.9 (A)-4 40 60 9300 1.5 (A)-5 4040 20 7000 1.6 (A)-6 40 20 20 20 15000 2.0 (A)-7 35 20 20 25 9600 1.6(A)-8 40 20 20 20 9000 1.8 (A)-9 40 50 10 10000 2.0 (A)-10 30 50 2012000 2.0 (A)-11 30 30 40 12000 2.0

The resin (A)-2′ was further reacted with chloromethoxymethane tosubstitute some of the hydrogen atoms of the hydroxyl groups within theresin (A)-2′ with methoxymethyl groups, thereby obtaining a resin (A)-2.As a result of measuring the resin (A)-2 by proton NMR, it was foundthat 40 mol % of the hydroxyl groups of the resin (A)-2′ have beensubstituted with methoxymethyl groups.

The structures of resins (A)-1 to (A)-11 are shown below.

In the formulas, the subscript numerals at the lower right of theparentheses indicate the ratio (mol %) of the structural units.

Further, in formula (A)-2, each R represents a hydrogen atom or amethoxymethyl group, wherein 40% of R within the resin (A)-2 aremethoxymethyl groups.

Examples 1 to 40 and Comparative Examples 1 to 5

The components shown in Tables 2 to 4 were mixed and dissolved to obtainpositive resist composition solutions.

In Tables 2 to 4, the reference characters indicate the following.Further, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added.

(B)-1: (4-methylphenyl)diphenylsulfonium nonafluorobutanesulfonate

(D)-1: tripentylamine

(S)-1: a mixed solvent of PGMEA/PGME=6/4 (weight ratio)

Using the obtained positive resist composition solutions, the followingevaluations were performed.

<Measurement of Contact Angle>

Using FACE contact angle meter, model CA-X150 (product name;manufactured by Kyowa Interface Science Co., Ltd.), the contact angle,the sliding angle and the receding angle were measured in the followingmanner.

Firstly, a positive resist composition solution was applied onto an8-inch silicon wafer using a spinner, and was heated at 95° C. for 90seconds to thereby form a resist film having a thickness of 175 nm.Then, the resist film in a horizontal state was contacted with the amicrosyringe equipped on the contact angle meter (whereby 2 μL of purewater was droppped from the microsyringe), and the contact angle(contact angle to water) was measured with respect to a droplet on theresist film (measurement of contact angle prior to exposure).

Further, a resist film was formed in the same manner as described above,and the contact angle (contact angle to water) was measured insubstantially the same manner as described above, except that an openframe exposure (exposure without a mask) was performed using a simpleexposure apparatus VUVES4500 (manufactured by Lintec Japan Corporation)with an ArF excimer laser (193 nm) (measurement of contact angle afterexposure).

The results are shown in Tables 2 to 4.

<Measurement of Receding Angle and Sliding Angle>

The obtained positive resist composition solution was applied onto an8-inch silicon wafer using a spinner, and was prebaked on a hot plate at110° C. for 90 seconds to thereby form a resist film having a thicknessof 175 nm. Then, one droplet (50 μl) of pure water was droppped onto theresist film, and the receding angle and the sliding angle were measuredusing the apparatus under conditions as described below (measurement ofreceding angle and sliding angle prior to exposure).

Further, a resist film was formed in the same manner as described above,and the receding angle and the sliding angle were measured insubstantially the same manner as described above, except that an openframe exposure (exposure without a mask) was performed using a simpleexposure apparatus VUVES4500 (manufactured by Lintec Japan Corporation)with an ArF excimer laser (193 nm) (measurement of receding angle andsliding angle after exposure).

The results are shown in Tables 2 to 4.

<Name of Apparatus>

AUTO SLIDING ANGLE: SA-30 DM (manufactured by Kyowa Interface ScienceCo. Ltd.)

AUTO DISPENSER: AD-31 (manufactured by Kyowa Interface Science Co. Ltd.)

<Analysis Software>

FAMAS

As shown in the results below, in Examples 1 to 10 in which the resin(A)-1 classified as the resin (A2) was used in combination with theresins (A)-2 to (A)-4 classified as the resin (A1), the contact angleand receding angle prior to exposure were large as compared to those inComparative Example 1 in which only resin (A)-1 was used, and thesliding angle was the same or smaller than that in ComparativeExample 1. Further, in Examples 1 to 10, the contact angle and recedingangle after exposure were also large as compared to those in ComparativeExample 1.

Furthermore, in Examples 11 to 40 in which the resin (A)-5 classified asthe resin (A2) was used in combination with the resins (A)-6 to (A)-11classified as the resin (A1), the contact angle and receding angle priorto and after exposure were large as compared to that in ComparativeExample 5 in which only the resin (A)-5 was used. Further, in Examples11 to 40, the sliding angle after exposure was the same or smaller thanthat in Comparative Example 5.

TABLE 2 Contact angle (°) Sliding angle (°) Receding angle (°) ComponentComponent Component Prior to After Prior After Prior to After Component(A) (B) (D) (S) exposure exposure to exposure exposure exposure exposureComp. Ex. 1 (A)-1 — (B)-1 (D)-1 (S)-1 64.5 64.5 25.5 29.0 50.7 47.6[100]  [4.0] [0.4] [1350] Comp. Ex. 2 — (A)-2 (B)-1 (D)-1 (S)-1 86.179.5 17.0 21.0 76.8 70.8 [100]  [4.0] [0.4] [1350] Example 1 (A)-1 (A)-2(B)-1 (D)-1 (S)-1 85.1 81.8 17.5 21.0 75.2 71.9 [75] [25]  [4.0] [0.4][1350] Example 2 (A)-1 (A)-2 (B)-1 (D)-1 (S)-1 84.7 85.8 17.5 16.0 75.976.7 [90] [10]  [4.0] [0.4] [1350] Example 3 (A)-1 (A)-2 (B)-1 (D)-1(S)-1 76.2 77.3 23.5 24.0 63.3 63.2 [99] [1] [4.0] [0.4] [1350] Example4 (A)-1 (A)-2 (B)-1 (D)-1 (S)-1 67.2 66.8 24.5 28.0 53.3 50.3   [99.9]  [0.1] [4.0] [0.4] [1350] Comp. Ex. 3 — (A)-3 (B)-1 (D)-1 (S)-1 88.195.2 13.0 13.0 88.1 87.9 [100]  [4.0] [0.4] [1350] Example 5 (A)-1 (A)-3(B)-1 (D)-1 (S)-1 81.9 81.5 21.0 23.0 68.1 65.7 [95] [5] [4.0] [0.4][1350] Example 6 (A)-1 (A)-3 (B)-1 (D)-1 (S)-1 72.8 73.4 23.0 26.5 59.656.8 [99] [1] [4.0] [0.4] [1350] Example 7 (A)-1 (A)-3 (B)-1 (D)-1 (S)-166.6 66.5 25.0 22.5 52.3 54.5   [99.9]   [0.1] [4.0] [0.4] [1350] Comp.Ex. 4 — (A)-4 (B)-1 (D)-1 (S)-1 88.8 89.3 11.0 11.0 83.5 82.7 [100] [4.0] [0.4] [1350] Example 8 (A)-1 (A)-4 (B)-1 (D)-1 (S)-1 85.2 85.815.0 17.0 74.7 73.2 [95] [5] [4.0] [0.4] [1350] Example 9 (A)-1 (A)-4(B)-1 (D)-1 (S)-1 70.8 70.4 23.5 27.0 56.5 54.4 [99] [1] [4.0] [0.4][1350] Example 10 (A)-1 (A)-4 (B)-1 (D)-1 (S)-1 66.4 66.8 26.0 29.0 51.948.5   [99.9]   [0.1] [4.0] [0.4] [1350]

TABLE 3 Contact angle (°) Sliding angle (°) Receding angle (°) ComponentComponent Component Prior to After Prior After Prior After Component (A)(B) (D) (S) exposure exposure to exposure exposure to exposure exposureComp. Ex. 5 (A)-5 — (B)-1 (D)-1 (S)-1 66.6 68.7 23.5 32.0 53.2 50.0[100]  [4.0] [0.4] [1350] Example 11 (A)-5 (A)-6 (B)-1 (D)-1 (S)-1 83.381.7 19.0 23.5 70.4 65.5 [50] [50] [4.0] [0.4] [1350] Example 12 (A)-5(A)-6 (B)-1 (D)-1 (S)-1 79.3 78.6 21.0 24.5 66.1 62.4 [80] [20] [4.0][0.4] [1350] Example 13 (A)-5 (A)-6 (B)-1 (D)-1 (S)-1 74.8 74.8 21.526.0 63.4 57.6 [90] [10] [4.0] [0.4] [1350] Example 14 (A)-5 (A)-6 (B)-1(D)-1 (S)-1 71.5 71.3 23.0 28.0 58.2 53.4 [95]  [5] [4.0] [0.4] [1350]Example 15 (A)-5 (A)-6 (B)-1 (D)-1 (S)-1 67.7 68.9 23.5 30.0 54.2 50.5[99]  [1] [4.0] [0.4] [1350] Example 16 (A)-5 (A)-7 (B)-1 (D)-1 (S)-183.4 84.5 21.0 23.0 72.5 68.5 [50] [50] [4.0] [0.4] [1350] Example 17(A)-5 (A)-7 (B)-1 (D)-1 (S)-1 82.5 82.9 20.0 24.0 70.3 65.9 [80] [20][4.0] [0.4] [1350] Example 18 (A)-5 (A)-7 (B)-1 (D)-1 (S)-1 78.9 78.522.0 25.5 64.7 61.6 [90] [10] [4.0] [0.4] [1350] Example 19 (A)-5 (A)-7(B)-1 (D)-1 (S)-1 75.0 74.5 23.0 28.5 61.2 56.9 [95]  [5] [4.0] [0.4][1350] Example 20 (A)-5 (A)-7 (B)-1 (D)-1 (S)-1 69.5 70.2 23.5 29.5 56.451.2 [99]  [1] [4.0] [0.4] [1350] Example 21 (A)-5 (A)-8 (B)-1 (D)-1(S)-1 73.5 73.5 25.0 27.0 60.7 59.0 [50] [50] [4.0] [0.4] [1350] Example22 (A)-5 (A)-8 (B)-1 (D)-1 (S)-1 71.7 72.4 25.0 30.0 59.4 55.7 [80] [20][4.0] [0.4] [1350] Example 23 (A)-5 (A)-8 (B)-1 (D)-1 (S)-1 70.6 70.725.0 30.0 57.9 53.3 [90] [10] [4.0] [0.4] [1350] Example 24 (A)-5 (A)-8(B)-1 (D)-1 (S)-1 68.9 69.1 25.0 31.0 55.8 51.1 [95]  [5] [4.0] [0.4][1350] Example 25 (A)-5 (A)-8 (B)-1 (D)-1 (S)-1 68.3 82.3 27.0 32.5 53.650.3 [99]  [1] [4.0] [0.4] [1350]

TABLE 4 Contact angle (°) Sliding angle (°) Receding angle (°) ComponentComponent Component Prior to After Prior After Prior After Component (A)(B) (D) (S) exposure exposure to exposure exposure to exposure exposureExample 26 (A)-5 (A)-9 (B)-1 (D)-1 (S)-1 75.0 74.5 23.0 29.5 60.8 54.9[50] [50] [4.0] [0.4] [1350] Example 27 (A)-5 (A)-9 (B)-1 (D)-1 (S)-171.3 70.9 24.0 29.5 57.1 52.7 [80] [20] [4.0] [0.4] [1350] Example 28(A)-5 (A)-9 (B)-1 (D)-1 (S)-1 70.0 68.8 24.0 30.5 55.8 51.0 [90] [10][4.0] [0.4] [1350] Example 29 (A)-5 (A)-9 (B)-1 (D)-1 (S)-1 68.5 69.025.0 32.0 54.4 50.5 [95]  [5] [4.0] [0.4] [1350] Example 30 (A)-5 (A)-9(B)-1 (D)-1 (S)-1 67.9 68.7 25.5 32.0 53.5 50.1 [99] [1] [4.0] [0.4][1350] Example 31 (A)-5 (A)-10 (B)-1 (D)-1 (S)-1 76.5 75.4 25.0 27.560.4 58.4 [50] [50] [4.0] [0.4] [1350] Example 32 (A)-5 (A)-10 (B)-1(D)-1 (S)-1 72.7 73.8 26.0 29.5 58.1 54.6 [80] [20] [4.0] [0.4] [1350]Example 33 (A)-5 (A)-10 (B)-1 (D)-1 (S)-1 71.9 71.6 26.0 31.0 57.4 52.4[90] [10] [4.0] [0.4] [1350] Example 34 (A)-5 (A)-10 (B)-1 (D)-1 (S)-170.1 69.3 25.0 31.0 55.5 52.5 [95]  [5] [4.0] [0.4] [1350] Example 35(A)-5 (A)-10 (B)-1 (D)-1 (S)-1 68.5 68.9 25.0 32.0 53.5 50.3 [99]  [1][4.0] [0.4] [1350] Example 36 (A)-5 (A)-11 (B)-1 (D)-1 (S)-1 78.3 78.123.0 26.5 65.0 61.7 [50] [50] [4.0] [0.4] [1350] Example 37 (A)-5 (A)-11(B)-1 (D)-1 (S)-1 76.7 77.4 23.5 28.0 64.6 60.0 [80] [20] [4.0] [0.4][1350] Example 38 (A)-5 (A)-11 (B)-1 (D)-1 (S)-1 75.7 75.6 23.5 28.563.4 59.5 [90] [10] [4.0] [0.4] [1350] Example 39 (A)-5 (A)-11 (B)-1(D)-1 (S)-1 73.4 75.0 23.5 29.0 61.1 57.0 [95]  [5] [4.0] [0.4] [1350]Example 40 (A)-5 (A)-11 (B)-1 (D)-1 (S)-1 73.0 74.4 23.5 31.0 59.3 54.6[99]  [1] [4.0] [0.4] [1350]

<Lithography Properties>

An organic anti-reflection film composition (product name: ARC-29,manufactured by Brewer Science Ltd.) was applied onto the surface of an8-inch silicon wafer using a spinner, and the composition was then bakedat 205° C. for 60 seconds, thereby forming an organic anti-reflectionfilm having a thickness of 77 nm.

The positive resist composition solution obtained above was applied ontothe surface of the anti-reflection film using a spinner, and was thenprebaked (PAB) on a hotplate at 120° C. for 90 seconds and dried,thereby forming a resist film having a film thickness of 175 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern, using an ArF exposureapparatus NSR-S302 (manufactured by Nikon Corporation, NA (numericalaperture)=0.60, ⅔ annular illumination).

Thereafter, a PEB treatment was conducted at 120° C. for 90 seconds,followed by development for 30 seconds at 23° C. in a 2.38% by weightaqueous solution of tetramethylammonium hydroxide. Then, the resist waswashed for 30 seconds with pure water, followed by drying by shaking,thereby forming a 120 nm line and space (1:1) resist pattern (hereafterreferred to as a L/S pattern).

The thus formed L/S patterns were observed by SEM. As a result, it wasfound that the L/S patterns formed by using the positive resistcompositions of Examples 1 to 40 and Comparative Example 1 exhibitedsubstantially the same lithography properties.

On the other hand, with respect to the positive resist compositions ofComparative Example 2 in which only the resin (A)-2 was used andComparative Example 3 in which only the resin (A)-3 was used, it wasfound that, although resist patterns were resolved, the thickness lossof the patterns was extremely poor. With respect to the positive resistcomposition of Comparative Example 4 in which only the resin (A)-4 wasused, a resist pattern could not be resolved.

<Evaluation of Eluted Substance>

Using the positive resist composition solutions of Example 8 andComparative Example 1, resist films were formed in the same manner asdescribed above. Then, using VRC310S (manufactured by S.E.S CO., LTD.),one droplet of pure water (150 μl) was moved from the center of thewafer in a circular manner at room temperature at a constant linearvelocity (area: 221.56 cm²). Thereafter, the droplet was collected, andanalyzed by an analyzing apparatus Agilent-HP1100 LC-MSD (manufacturedby Agilent Technologies), and the amounts of elution (mol/cm²) of thecation moiety (PAG+) and anion moiety (PAG−) of the component (B) weredetermined.

Further, resist films were formed in the same manner as described above.Then, an open frame exposure (exposure without a mask) was performedusing a simple exposure apparatus VUVES4500 (manufactured by LintecJapan Corporation) with an ArF excimer laser (193 nm).

Subsequently, the exposed resist film was analyzed in the same manner asdescribed above, and the amounts of elution (mol/cm²) of the cationmoiety (PAG+) and anion moiety (PAG−) of the component (B) weredetermined.

The results are shown in Table 5.

TABLE 5 Amount of elution (×10⁻¹² mol/cm²) Prior to exposure Afterexposure PAG+ PAG− PAG+ PAG− Comp. Ex. 1 13.26 23.6 0.94 45.6 Example 83.91 12.1 0.15 28.7

As seen from the results shown above, when the positive resistcomposition of Example 8 using a combination of the resin (A)-1 and theresin (A)-4 was used, elution of the component (B) into the immersionmedium (water) was suppressed prior to and after exposure, and hence,the effect of suppressing elution was confirmed. On the other hand, whenthe positive resist composition of Comparative 1 using the resin (A)-1alone was used, elution of the component (B) into the immersion medium(water) was conspicuously observed prior to and after exposure.

In the above-described evaluations, the “amount of elution prior toexposure” is for evaluating the amount of elution at unexposed portionsof the resist film during the formation of a resist pattern by selectiveexposure. Further, the “amount of elution after exposure” is forevaluating the amount of elution at the exposed portions. Therefore,since the amount of a substance eluted into the immersion medium (water)was small both prior to and after exposure, it was confirmed that thepositive resist composition of Example 8 exhibited an excellentresistance to an immersion medium, and hence, the positive resistcomposition can be preferably used in a method of forming a resistpattern including an immersion exposure step.

Further, as seen from the results shown above, the contact angle and thereceding angle increase by using the resin (A1) in combination with theresin (A2), and the levels of the contact angle and the receding anglecorrelate with the effect of suppressing the elution of a substance.

Therefore, it is evident that the resist composition of the presentinvention in which the resin (A1) is used in combination with the resin(A2) and the content of the resin (A1) within the component (A) is from0.1 to 50% by weight can achieve both of excellent resistance to animmersion medium and excellent lithography properties, and hence, theresist composition can be preferably used for immersion exposure.

INDUSTRIAL APPLICABILITY

The resist composition of the present invention can achieve both ofexcellent resistance to an immersion medium and excellent lithographyproperties, and hence, the resist composition can be preferably used forimmersion exposure and a method of forming a resist pattern.

What is claimed is:
 1. A resist composition for immersion exposurecomprising a resin component (A) which exhibits changed alkalisolubility under action of acid and an acid-generator component (B)which generates acid upon irradiation, wherein said resin component (A)comprises a resin (A1) which has a structural unit (a) derived fromacrylic acid containing a fluorinated hydroxyalkyl group represented bygeneral formula (I) shown below and a structural unit (a1) selected fromthe group consisting of structural units represented by general formulas(a1-0-1) and (a1-0-2) shown below,

wherein x represents an integer of 0 to 5; and y and z eachindependently represents an integer of 1 to 5,

wherein, R represents a hydrogen atom, halogen atom, lower alkyl group,or halogenated lower alkyl group; and X¹ represents an acid dissociable,dissolution inhibiting group,

wherein, R represents a hydrogen atom, halogen atom, lower alkyl group,or halogenated lower alkyl group; X² represents an acid dissociable,dissolution inhibiting group; and Y² represents an alkylene group or analiphatic cyclic group; and a resin (A2) which has a structural unit(a′) derived from acrylic acid and contains no fluorine atom, whereinthe amount of said resin (A1) contained in said resin component (A) iswithin a range from 0.1 to 20% by weight.
 2. The resist composition forimmersion exposure according to claim 1, wherein said resin component(A1) has a structural unit (a0) derived from an acrylic ester having onthe side chain portion thereof a fluorinated hydroxyalkyl group and analiphatic monocyclic/polycyclic group.
 3. The resist composition forimmersion exposure according to claim 2, wherein said structural unit(a0) comprises at least one member selected from the group consisting ofstructural units represented by general formulas (a0-1) to (a0-3) shownbelow:

wherein R represents a hydrogen atom, an alkyl group, a halogen atom ora halogenated alkyl group; R²¹ represents an aliphatic cyclic grouphaving a valency of (e+1); R²² and R²³ each independently represents ahydrogen atom or a monovalent aliphatic cyclic group, with the provisothat at least one of R²² and R²³ represents an aliphatic cyclic group;a, d and f each independently represents an integer of 0 to 5; b and ceach independently represents an integer of 1 to 5; and e represents 2or
 3. 4. The resist composition for immersion exposure according toclaim 1, wherein said resin (A1) further comprises a structural unit(a2) derived from an acrylate ester having a lactone-containing cyclicgroup.
 5. The resist composition for immersion exposure according toclaim 1, wherein said resin (A1) further comprises a structural unit(a3) derived from an acrylate ester having a polar group-containingaliphatic hydrocarbon group.
 6. The resist composition for immersionexposure according to claim 1, wherein said resin (A2) has a structuralunit (a′ 1) derived from an acrylate ester containing no fluorine atomand having an acid dissociable, dissolution inhibiting group.
 7. Theresist composition for immersion exposure according to claim 6, whereinsaid resin (A2) further comprises a structural unit (a′2) derived froman acrylate ester containing no fluorine atom and having alactone-containing cyclic group.
 8. The resist composition for immersionexposure according to claim 6, wherein said resin (A2) further comprisesa structural unit (a′3) derived from an acrylate ester containing nofluorine atom and having a polar group-containing aliphatic hydrocarbongroup.
 9. The resist composition for immersion exposure according toclaim 1, further comprising a nitrogen-containing organic compound (D).10. A method of forming a resist pattern, comprising: applying a resistcomposition for immersion exposure of claim 1 to a substrate to form aresist film on the substrate; subjecting said resist film to immersionexposure; and developing said resist film to form a resist pattern.